Pump.



E. W. CASH.

PUMP.

APPLICATION FILED DBO. 28, 1912,

1,085,666. Patented Feb. 3, 1914.

WITNESSES:

. l/VVE/VTUR -ff accau: By

A TTOR/VEY COLUMBIA PLANOGRAPH co wAsmNa'row, n. c

ERNEST WILLIAM CASH, 0F HAMPTON WICK, ENGLAND.

PUMP.

Specification of Letters Patent.

Patented Feb. 3,1914.

Application filed December 28, 1912. Serial No. 738,987.

To all whom it may concern Be it known that I, ERNEST WILLIAM CASH, a citizen of Great Britain, residing at 26 Cedar road, Hampton Wick, in the county of Middlesex, England, engineer, have invented new and useful Improvements in Pumps, of which the following is a specification.

My invention relates to improvements in pumps of the type used in systems for measuring the speed of vehicles or other objects.

The object of this invention is to provide a valveless pump for operating speed indicaters, in which the number of working parts is reducedto a minimum and secondly, to provide a valveless pump so constructed that the compression is substantially reduced and the consequent heating of the cylinder avoided so that the amount of air drawn by the pump from the indicator ateaclr stroke will be. the same both at starting and when it has been at work for 20 to 30 minutes or longer.

I attain these objects by the mechanism shown in the accompanying drawings which illustrate my invention, Figure 1 being a front elevation partly in section. Fig. 2 is a sectional elevation through the axis of the crank shaft. l p y The same letters apply. to the same parts in both drawings.

In carrying my invention into effect according to the illustrations, I provide a vertical cylinder, A, cast or fixed to the top of an inclosed crankcase B, the cylinder opening into the crank case, one side of the latter being closed by the door C, Fig. 2 which engages and is secured to lugs provided in the crankcase and supports one end of the crankshaft bearings.

The cylinder is fitted with a piston D, big. 1. In the side of the cylinder, I provide a port E, Fig. 2, which is connected by a pipe to the speed indicator. Adjacent to the head of the cylinder, I provide an exhaust port F, Fig. l which I connect by passage with a port G formed in the wall of the cylinder about the middle of its length. The piston receives its motion through a connecting rod H which is attached to the crankshaft I, as shown in Fig. 2 which is driven by gearing or other means operated by the vehicle or other object, the speed of which is to be measured. In case of an automobile, the pump is attached to the axle and is driven by gearing fixed to a wheel. The

head of the piston is fitted with rings to make it tight and efiect-ive in its chamber.

Formed in the piston, from a point opposite the port G, when the piston is at the top of its stroke, to a point below the bottom of the cylinder, is a fiat or straight groove J, Fig. 1, which communicates with the interior of the crank ease. From the above mentioned point opposite the port, G, I extend the flat groove upward for a distance equal to from a quarter to one half the length of the stroke, but I prefer to make it one third the length of the stroke, and to make the area of the opening caused by the groove or flat gradually diminishing to nothing at its uppermost end as shown.

At the base of the cylinder, I provide a boss K, Fig. l bored to receive a felt or other suitable lubricating pad, L, which is pressed against the side of the piston by the screw cap, M, the pad being supplied with oil from a siphon lubricator N.

The operation of my invention as illustrated, is as follows :-Assuming the piston to be at the bottom of its stroke, the exhaust port, G is then closed, and in traveling upward the piston first covers the port E, Fig. 2 communicating with the speed indicator and commences to compress the air in the cylinder until the port G is opened very slightly by the top of the diminished groove which relieves the pressure in the cylinder before it causes heating, the air being discharged through the opening caused by the flat or groove J to the crankcase thence to the atmosphere. On the return stroke of the piston the port G is gradually closed by the diminishing area of the groove J. The flow of air into the cylinder is thus gradually restricted until the port G is closed. After the port G is closed, a partial vacuum is created behind the piston until the port E connected with the speed indicator is uncovered and the air from the indicator flows into the cylinder to equalize the pressure. Thus each stroke of the piston removes a certain amount of air from the speed indi-' cator and produces therein a vacuum, the amount of which is proportional to the speed of the pump.

The tapering groove formed in the piston does not reduce the efficiency of the pump as when it begins to uncover the port G on the compression stroke the pressure in the cylinder is higher than that of the atmosphere, whereas on the downward stroke the difference in pressure between the atmosphere and that in the top of the cylinder is small, and consequently the speed of the air passing into the cylinder through port G is very low until the port is completely covered.

The method of lubricating the piston described above, by using suitable oil, insures a constant lubrication to the piston thus preventing a difference in the amount of air drawn by the pump at different strokes due to a varying amount of oil on the piston.

Although I have described my invention as applied to a single cylinder pump, it is obvious that it can be applied to pumps with two or more cylinders. I may also combine the improved vacuum pump to operate speed indicators as described above, with a pulsating pump for operating a distance recorder.

What I claim is:

1. In a pump, the combination with the cylinder thereof, a piston located in the cylinder and formed with an inclinedshaped surface in the side thereof, the wall of the cylinder having an exhaust port formed in and located adjacent the head end, and a second port formed in the wall of the cylinder at substantially midway of its length, and a passageway connecting the two ports, the head end of the cylinder also having a second port designed to be connected to a closed chamber, whereby, when the piston is operated and the inclinedsbaped surface sweeps past the last-named port, the pressures at the two ends of the piston will be equalized, as described, and whereby a partial vacuum may be formed in the chamber that is connected to the second port before the pressures at the two ends of the piston are equalized.

2. A vacuum pump, comprising, in combination with the cylinder, a piston therein formed with a flat, tapered surface in the side thereof, its tapered end extending toward the head-end of the cylinder, two exhaust ports in the wall of the cylinder connected by a passage-way, one of the ports located to register with the flat, tapered surface of the piston and the other port located adjacent the head-end, and a third port in the wall of the cylinder adjacent the headend and designed to be connected to a chamber from which the air is to be exhausted.

3. A pump designed to produce a partial vacuum and comprising a cylinder, a crank casing member, a piston in the cylinder and having a portion of its length grooved, there being three ports in the cylinder wall, two located adjacent the head-end and one located substantially midway of the length of the cylinder and designed to register with the groove in the piston, one of the ports in the head-end having a connection with a passageway that extends to the last-named port to equalize the pressures at the opposite ends of the piston at a predetermined point in the travel of the piston and after a partial vacuum is produced in the head-end of the cylinder, the other port adjacent the head-end being designed to be connected to a chamber in which a partial vacuum is desired, as described. 1

4:. A pump designed to produce a partial vacuum and comprising a cylinder-member formed with a plurality of ports therein, a piston having an inclined surface and located in the cylinder, said surface designed and arranged to register with one of the ports which is connected with a port adj acent the head-end of the cylinder to gradually equalize the pressures as the piston travels from one end of the cylinder to the other, and whereby a partial vacuummay be produced in the head-end of the cylinder'prior to registration'of the inclined surface with the said port, as described.

Dated this the 12th day of December,

ERNEST WILLIAM CASH. Vitnesses:

THOMAS YOUNG, S. W. PHELPS.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

' Washington, I). C. 

